Bird flu or avian influenza

Avian influenza: bird flu and avian flu

Through this page, you can stay up to date about the latest developments on avian influenza. Wageningen Bioveterinary Research (WVBR) takes care of diagnostics in The Netherlands.

What is avian influenza?

Bird flu or avian influenza (AI) is a collective term for different influenza viruses that may be dangerous to poultry. Especially chickens, turkeys, waterfowl, waders, beach birds, ratites and starlings are susceptible to avian influenza, with possible lethal consequences. Some forms are also transmissible to humans.

Mild and hazardous avian influenza

Avian influenza has two variants: a mild variant and a hazardous variant. Most viruses are the mild variant, known as low pathogenic avian influenza (LPAI). On average about 10 to 30 introductions of the mild variant are detected annually. Birds that have been infected with this variant exhibit few disease symptoms. However, the mild form of H5 or H7 bird flu may also change into the highly contagious variant, known as high pathogenic avian influenza (HPAI). It is for this reason that companies are also culled in the case of an outbreak of a mild variant H5 or H7 bird flu.

Bird flu in the Netherlands 2016/2017

In late 2016 and early 2017, besides wild birds, several poultry farms and household flocks were found to be infected with the highly pathogenic variant of avian influenza. Research has shown that these infections were linked to wild migratory birds.

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Infection and spread

Wild birds are often the source of avian influenza viruses. Birds, including poultry, can catch bird flu in several ways:

  • Through direct contact with infected birds; the virus can be spread through the respiratory system, eye fluids and droppings
  • Through contaminated materials such as food, crates, vehicles and people who have been in contact with the virus through their shoes or clothing
  • Via dust from a contaminated coop (spread through the air)

Transmission to humans and bird flu symptoms

In some cases people – and other mammals like pigs and foxes – can become infected. This can happen if there is direct and extensive contact between infected animals and humans, like the caretakers of the animals or those involved in culling.

The symptoms of avian influenza in humans are very mild in most cases. Serious or even fatal infections have only been reported in exceptional cases. This happened for example after infection with the HPAI H5N1 virus in Asia in 1997 and 2004, with a HPAI H7N7 in the Netherlands in 2003 and recently with a LPAI H7N9 virus in China.

The virus can enter the Netherlands through the import of live birds, eggs and egg products, poultry and poultry products as well as through travellers. Spreading via migratory birds also represents a risk.

Free-range poultry farms in the Netherlands are at greater risk of an avian influenza infection, because the poultry can come into direct contact with potentially infected wild birds and waterfowl.


There is a fear that the virus will change to make it easily transmissible among humans. This could lead to a worldwide influenza epidemic; a pandemic. Whether this will actually happen is unpredictable. Previous flu pandemics were the Spanish flu (1918), with an estimated 40 million deaths worldwide, the Asian flu (1957-58) and the Hong Kong flu (1968) with 2 to 3 million victims each.

Measures and solutions

Hygiene measures

Within the European Union legislation exists to prevent avian influenza from being introduced or spread throughout the EU via infected poultry or transport. For example, farmers and transporters of live animals must take hygienic measures to prevent infection and the spread of the virus.

Monitoring and early warning program

The Netherlands has operated a monitoring program since the HPAI H7N7 outbreak in 2003. Domestic poultry, but also wild birds, are regularly checked for antibodies to the virus. In this way, it is possible to discover avian influenza at an early stage and limit the spread of the virus (early warning programs).

Vaccination of poultry?

Vaccination of poultry is possible but there are many snags. It is costly, difficult to organise and tied to permits. Some buyers of Dutch poultry products (including Germany) do not want products from vaccinated animals.

Links and FAQ

Publications 2020

Publications 2019

Publications 2018

Publications 2017

Publications 2016